Very good game and impressive if you have no prior game dev experience!
- There is no sense of progression in the game. At the start the enemies feel quite un-killable and you have no shoot cooldown. I don't feel the game getting harder either when the wave number increases. What I would recommend is you have the enemies start out weak, slow, and low in numbers, and you increase the numbers as the rounds progress.
- Also I kind of found it disappointing when the game suddenly ended after 5 rounds. I would find it more fitting to have it continue endlessly, becoming harder and harder until you fail. If the intention was to make just 5 rounds, then the score should probably not be displayed because it's irrelevant in that case.
- I don't know if it was a bug or by design but the enemies de-spawned after some time.
Other than that the game is fun (and strange :D ).